DESCRIPTION: The goal of this project is to develop two simple sensitive and accurate immunologic methods to quantify hemoglobin F. One method will enumerate and identify the erythrocytes and reticulocytes containing hemoglobin F and the other would quantify the percentage of hemoglobin F in blood hemolysates. The development of these kits is facilitated in this laboratory by the availability of monoclonal antibodies against hemoglobin F. This obviously permits the development of better methods than the cytologic acid elution method of Kleihauer or the alkaline precipitation methods of Betke. Thus, using available antibody, the Investigator plans to develop a enzyme link immunoabsorbent assay (ELISA) to quantify the absolute level of hemoglobin F in red blood cell lysates and secondly to develop a fluorochrome conjugated immunoassay to specifically enumerate the intact red blood cells which produce hemoglobin F. The kits will be developed which could use either flow cytometry and/or fluorescence microscopy to enumerate hemoglobin F cells in the fluorochrome conjugated immunoassay. The latter methodology would permit measurements of the relative proportion of reticulocytes containing Hb F if dual staining was used or studies of the nature of the other Hb molecules which share the same erythrocytes with Hb F and the relative amounts of Hb F within individual cells. A simple assay such as those described would be highly useful in drug studies developed to increase hemoglobin F synthesis to ameliorate the severity of sickle cell disease.Likewise, it may be useful in studies which were desired to determine the number of fetal nucleated red cells that entered the maternal circulation.